Lubricating Composition

ABSTRACT

The present invention relates to a lubricating composition containing a dispersant, a corrosion inhibitor and an antioxidant. The invention further provides a method for lubricating a mechanical device with the lubricating composition.

FIELD OF INVENTION

The present invention relates to a lubricating composition containing a dispersant, a corrosion inhibitor and an antioxidant. The invention further provides a method for lubricating a mechanical device, typically requiring a working fluid, a hydraulic fluid, a circulating oil or a turbine oil, with the lubricating composition.

BACKGROUND OF THE INVENTION

Ash-containing and ashless lubricating compositions are utilised in various mechanical devices (for example stationary or mobile machinery requiring a working fluid, a hydraulic fluid, a circulating oil or a turbine oil). The lubricating compositions often operate under high temperatures and/or high pressure regimes in the mechanical device. The high temperatures and/or high pressure regimes are believed to decompose additives in the lubricating composition that are less thermally and/or oxidatively stable. Typically additives that tend to decompose are often ash-containing additives that contain a metal. Furthermore, as ash-containing additives decompose, divalent metals such as zinc, calcium or magnesium, are released into the lubricating composition. The divalent metals are then capable of reacting with other performance additives present in the lubricating composition, such as alkenyl succinic anhydrides and alkenyl succinimides creating sludge and other particulate matter that can cause filter plugging.

In an attempt to overcome the difficulties associated with lubricating a mechanical device with ash-containing lubricating compositions, ashless formulations have been contemplated. However, the formulation of an ashless lubricating composition suitable for a mechanical device may be difficult and many compositions are believed to have at least one of limited oxidative stability, limited thermal stability, filter plugging, and produce unacceptable levels of sludge.

EP 0 821 053 A2 discloses a synergistic antioxidant composition composed of amine salts of alkyl phosphates and ethylene diamine, ammonium or metal salts of alkylarylsulphonates. The antioxidant composition is useful for zinc-free antiwear hydraulic fluids.

International Application WO 00/11122 discloses lubricating compositions containing (I) 100 pbw of a base oil, (II) an antiwear agent comprising (i) from 0.05 to 10 pbw of a phosphorothionate and from 0.01 to 1.0 pbw of an amine salt of phosphorus compound and/or (ii) from 0.05 to 10 pbw of a dithiophosphate, and (III) a rust preventing agent comprising from 0.01 to 1.0 pbw of an amide obtained by reacting a polyalkylene polyamine and a carboxylic acid having from 4 to 30 carbon atoms. The lubricating composition is suitable for hydraulic systems.

U.S. Pat. No. 5,922,657 discloses a hydraulic fluid containing a base oil selected from mineral, vegetable and synthetic oils, β-dithiophosphorylated propionic acid, and at least one oil additive from the group consisting of antioxidants, metal passivators, rust inhibitors, dispersants, detergents, viscosity index improvers, pour point depressants, antifoams, solid lubricants and further antiwear agents.

US Patent Application 2002/0010103 A1 discloses industrial oils such as hydraulic oils containing (a) at least one a compound selected from the group consisting of a phosphoric acid ester, a thiophosphoric acid ester, and amine salts thereof; (b) at least one of a phosphorus acid ester and/or an amine salt thereof; and (c) at least one compound selected from the group consisting of an alkenyl succinimide, an alkenyl succinic acid ester, benzylamine, and derivatives thereof.

International Application WO 04/113479 discloses industrial fluids containing (1) an antiwear package comprising: (a) a hydrocarbyl phosphate and amine salt thereof; and (b) an alkylene coupled adduct of a hydrocarbyl substituted dithiophosphoric acid and a α,β-unsaturated carbonyl containing compound; (2) an antioxidant package comprising: (a) a hydrocarbyl diphenylamine; and (b) a sterically hindered phenol; (3) a metal deactivator; and (4) an oil of lubricating viscosity.

Hence it would be desirable to discover a lubricating composition suitable for a mechanical device capable of reducing or minimising at least one of filter plugging, limited oxidative stability, limited thermal stability, and produce unacceptable levels of sludge. The present invention provides a lubricating composition and method of lubricating a mechanical device capable of reducing or minimising at least one of filter plugging, limited oxidative stability, limited thermal stability, and produce unacceptable levels of sludge.

SUMMARY OF THE INVENTION

In one embodiment the invention provides an ashless lubricating composition comprising:

(a) a dispersant;

(b) an antioxidant;

(c) a corrosion inhibitor; and

(d) an oil of lubricating viscosity.

In one embodiment the invention provides a method for lubricating a mechanical device (typically requiring a working fluid, a hydraulic fluid, a circulating oil or a turbine oil) comprising supplying to the mechanical device an ashless lubricating composition comprising:

(a) a dispersant;

(b) an antioxidant;

(c) a corrosion inhibitor; and

(d) an oil of lubricating viscosity.

In one embodiment the invention provides an ashless lubricating composition comprising:

(a) about 0.01 to about 2 wt % of a dispersant;

(b) about 0.01 to about 2 wt % of an antioxidant;

(c) about 0.0001 wt % to about 0.1 wt % of a corrosion inhibitor; and

(d) an oil of lubricating viscosity.

In one embodiment the invention provides a method for lubricating a mechanical device (typically requiring a working fluid, a hydraulic fluid, a circulating oil or a turbine oil) comprising supplying to the mechanical device an ashless lubricating composition comprising:

(a) about 0.01 to about 2 wt % of a dispersant;

(b) about 0.01 to about 2 wt % of an antioxidant;

(c) about 0.0001 wt % to about 0.1 wt % of a corrosion inhibitor; and

(d) an oil of lubricating viscosity.

In one embodiment the ashless lubricating compositions disclosed above further comprises an antiwear agent. In one embodiment the ashless lubricating compositions disclosed above further contain about 0.05 wt % to about 1.5 wt % of an antiwear agent.

In one embodiment the invention provides the ashless lubricating compositions disclosed above in the form of a concentrate.

DETAILED DESCRIPTION OF THE INVENTION

The present invention provides an ashless lubricating composition and a method for lubricating a mechanical device as disclosed above.

As used herein the term “ashless” means that the lubricating composition and/or additives discussed below are substantially-free of metal. Substantially-free of means the composition will contain ash-forming materials (e.g., a metal, typically a divalent metal such as zinc, calcium or magnesium) at less than about 150 ppm, or less than about 100 ppm, or about 10 ppm or less, or less than about 1 ppm. Typically, the ash-forming materials will be present only in trace amounts, normally associated with contaminants.

Dispersant

A suitable dispersant includes a succinimide dispersant (for example N-substituted long chain alkenyl succinimides), a Mannich dispersant, an ester-containing dispersant, a condensation product of a fatty hydrocarbyl monocarboxylic acylating agent with an amine or ammonia, an alkyl amino phenol dispersant, a hydrocarbyl-amine dispersant, a polyether dispersant, or a polyetheramine dispersant. In different embodiments the dispersant includes a succinimide dispersant, succinic acid ester dispersant, or Mannich dispersant.

In different embodiments the succinimide dispersant contains an average of at least about 8, or about 30, or about 35 up to about 350, or to about 200, or to about 100 carbon atoms. In one embodiment, the long chain alkenyl group is derived from a polyalkene characterised by an M _(n) (number average molecular weight) of at least 500. Generally, the polyalkene is characterised by an M _(n) of about 500, or about 700, (or about 800, or even about 900) to about 5000, (or to about 2500, or to about 2000, or to about 1500, or to about 1200). In one embodiment the long chain alkenyl group includes those derived from polyolefins. The polyolefins may be derived from monomers including mono-olefins having about 2 to about 10 carbon atoms, such as ethylene, propylene, 1-butene, isobutylene, and 1-decene. An especially useful monoolefin source is a C₄ refinery stream having about 35 to about 75 weight percent butene content and about 30 to about 60 weight percent isobutene content. Useful polyolefins include polyisobutylenes having a number average molecular weight of about 400 to about 5000, or about 400 to about 2500, or about 400, or about 500 to about 1500. The polyisobutylene vinylidene double bond content in different embodiments includes the ranges of about 5% to about 69%, or about 50% to about 69%, or about 50% to about 95%.

In one embodiment the succinimide dispersant comprises a polyisobutylene succinimide, wherein the polyisobutylene has a number average molecular weight of about 400 to about 5000.

Succinimide dispersants and their methods of preparation are more fully described in U.S. Pat. Nos. 4,234,435 and 3,172,892.

Suitable amines include mono amines or polyamines (for example ethylenediamine, diethylenetriamine, triethylenetetramine, pentaethylenehexamine, or still bottoms (commercially available from Dow as HPAX®)). The hydrocarbyl-substituted amine may be formed by heating a mixture of a chlorinated olefin or polyolefin such as a chlorinated polyisobutylene with an amine such as ethylenediamine in the presence of a base such as sodium carbonate as described in U.S. Pat. No. 5,407,453.

The dispersants may also be post-treated by conventional methods by a reaction with any of a variety of agents. Among these are boron-containing compounds, urea, thiourea, dimercaptothiadiazoles, carbon disulphide, aldehydes, ketones, carboxylic acids, hydrocarbon-substituted succinic anhydrides, maleic anhydride, nitriles, epoxides, phosphorus compounds and/or metal compounds. In one embodiment the dispersant is a borated dispersant. Typically the borated dispersant is derived from a succinimide dispersant comprising a polyisobutylene succinimide, wherein the polyisobutylene has a number average molecular weight of 400 to 5000.

A borated succinimide dispersant may be prepared using a borating agent. The borating agent includes various forms of boric acid (including metaboric acid, HBO₂, orthoboric acid, H₃BO₃, and tetraboric acid, H₂B₄O₇), boric oxide, boron trioxide, and alkyl borates, such as those of the formula (RO)_(x)B(OH)_(y) wherein x is about 1 to about 3 and y is about 0 to about 2, the sum of x and y being 3, and where R is an alkyl group containing about 1 to about 6 carbon atoms. In one embodiment, the boron compound is an alkali or mixed alkali metal and alkaline earth metal borate. These metal borates are generally hydrated particulate metal borates which are known in the art. In one embodiment the metal borates include mixed alkali and alkaline earth metal borates. The metal borates are available commercially.

In different embodiments the dispersant is present in ranges including about 0.001 wt % to about 5 wt %, or about 0.005 to about 2.5 wt %, about 0.05 to about 1.5 wt %, or about 0.08 to about 0.8 wt % of the lubricating composition.

Antioxidant

The antioxidant of the invention includes sulphurised olefins, sulphides such as tert-nonyl mercaptan reacted with propylene oxide (mole ratio 1:1), a hindered phenol, or aminic compounds such as phenylalphanaphthylamine or an alkylated diphenylamine.

Examples of a suitable hindered phenol include 2,6-di-tert-butyl-4-methylphenol, 3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionic acid butyl ester, 3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionic acid isooctyl ester or 3-(3,5-di-tert-butyl-4-hydroxy-phenyl)-propionic acid 2-ethylhexyl ester), 2,6-di-tert-butylphenol, 4-methyl-2,6-di-tert-butylphenol, 4-ethyl-2,6-di-tert-butylphenol, 4-propyl-2,6-di-tert-butylphenol, 4-butyl-2,6-di-tert-butylphenol 4-pentyl-2-6-di-tert-butylphenol, 4-hexyl-2,6-di-tert-butylphenol, 4-heptyl-2,6-di-tert-butylphenol, 4-(2-ethylhexyl)-2,6-di-tert-butylphenol, 4-octyl-2,6-di-tert-butylphenol, 4-nonyl-2,6-di-tert-butylphenol, 4-decyl-2,6-di-tert-butylphenol, 4-undecyl-2,6-di-tert-butylphenol, 4-dodecyl-2,6-di-tert-butylphenol, 4-tridecyl-2,6-di-tert-butylphenol, 4-tetradecyl-2,6-di-tert-butylphenol, or mixtures thereof.

Examples of a suitable methylene-bridged sterically hindered phenol include 4,4′-methylenebis(6-tert-butyl-o-cresol), 4,4′-methylenebis(2-tert-amyl-o-cresol), 2,2′-methylenebis(4-methyl-6-tert-butylphenol), 4,4′-methylene-bis(2,6-di-tertbutylphenol), or mixtures thereof.

Examples of a suitable aminic compound include nonyl diphenylamine, di-nonyl diphenylamine, octyl diphenylamine, di-octyl diphenylamine, butyl octyl diphenylamine, octyl styrenyl diphenylamine or diethyl dinonyl diphenylamine.

In one embodiment the antioxidant includes (i) a hindered phenol or (ii) an alkylated diphenylamine. In one embodiment the antioxidant includes a mixture of a hindered phenol and an alkylated diphenylamine.

In different embodiments the antioxidant is present in ranges including about 0.01 to about 3 wt %, or about 0.01 to about 2 wt %, or about 0.05 to about 1 wt % of the lubricating composition.

Corrosion Inhibitor

The corrosion inhibitor may also be described as a metal deactivator or a yellow-metal passivator.

Examples of a corrosion inhibitor include benzotriazoles, 1,2,4-triazoles, benzimidazoles, 2-alkyldithiobenzimidazoles, 2-alkyldithiobenzothiazoles, 2-(N,N-dialkyldithiocarbamoyl)benzothiazoles, 2,5-bis(alkyl-dithio)-1,3,4-thiadiazoles, 2,5-bis(N,N-dialkyldithiocarbamoyl)-1,3,4-thiadiazoles, 2-alkyldithio-5-mercapto thiadiazoles or mixtures thereof. In one embodiment the corrosion inhibitor includes a benzotriazole. In one embodiment the corrosion inhibitor includes a 2,5-bis(alkyl-dithio)-1,3,4-thiadiazole.

Benzotriazoles include those containing hydrocarbyl substitutions on at least one of the following ring positions 1- or 2- or 4- or 5- or 6- or 7-. The hydrocarbyl groups in different embodiments contain 1 to about 30, or 1 to about 15, or 1 to about 16 carbon atoms. In one embodiment the corrosion inhibitor includes tolyltriazole. In one embodiment hydrocarbyl benzotriazoles substituted at positions 4- or 5- or 6- or 7- are further reacted with an aldehyde and an amine.

Examples of suitable hydrocarbyl benzotriazoles further reacted with an aldehyde and an amine include N,N-bis(2-ethylhexyl)-ar-methyl-1H-benzotriazole-1-methanamine, N,N-bis(2-ethylhexyl)-4-methyl-1H-benzotriazole-1-methanamine, N,N-bis(2-ethylhexyl)-4-methyl-1H-benzotriazole-1-methanamine, 2H-benzotriazole-2-methanamine, N-(4-methoxyphenyl)-1H-benzotriazole-1-methanamine, N,N-didodecyl-1H-benzotriazole-1-methanamine, N-(1H-benzotriazol-1-ylmethyl)-N-(2-ethylhexyl)-1H-benzotriazole-1-methanamine, N-methyl-N-phenyl-1H-benzotriazole-1-methanamine, 4,5,6,7-tetrahydro-N,N-ditridecyl-1H-benzotriazole-1-methanamine, N,N-dioctadecyl-1H-benzotriazole-1-methanamine, 5-methyl-N,N-dioctyl-1H-benzotriazole-1-methanamine, N,N-dibutyl-1H-benzotriazole-1-methanamine, N-(4-methylphenyl)-1H-benzotriazole-1-methanamine, N,N-bis(2-ethylhexyl)-1H-benzotriazole-1-methanamine, N,N-dioctyl-2H-benzotriazole-2-methanamine, N-dodecyl-1H-benzotriazole-1-methanamine, N-phenyl-1H-benzotriazole-1-methanamine, N,N-didodecyl-4,5,6,7-tetrahydro-1H-benzotriazole-1-methanamine, N,N-bis(2-ethylhexyl)-5-methyl-1H-benzotriazole-1-methanamine, N-octadecyl-1H-benzotriazole-1-methanamine, N,N-didodecyl-2H-benzotriazole-2-methanamine, N,N-dioctyl-1H-benzotriazole-1-methanamine, N-(2-ethylhexyl)-1H-benzotriazole-1-methanamine, 4,5,6,7-tetrahydro-N,N-ditetradecyl-1H-benzotriazole-1-methanamine, or mixtures thereof. In one embodiment the corrosion inhibitor includes N,N-bis(2-ethylhexyl)-4-methyl-1H-benzotriazole-1-methanamine or N,N-bis(2-ethylhexyl)-ar-methyl-1H-benzotriazole-1-methanamine.

In one embodiment, the corrosion inhibitor includes (i) a 2,5-bis(alkyl-dithio)-1,3,4-thiadiazole, (ii) a benzotriazole containing a hydrocarbyl substitution on at least one of the following ring positions 4- or 5- or 6- or 7-, or (iii) a benzotriazole containing a hydrocarbyl substitution (typically a benzotriazole further reacted with an aldehyde and an amine) at least one of the following ring positions 1- or 2-.

In one embodiment, the corrosion inhibitor includes 2,5-bis(alkyl-dithio)-1,3,4-thiadiazoles. In different embodiments the alkyl groups of 2,5-bis(alkyl-dithio)-1,3,4-thiadiazoles contain 1 to about 30, or about 2 to about 25, or 4 to about 20, or about 6 to about 16 carbon atoms. Examples of suitable 2,5-bis(alkyl-dithio)-1,3,4-thiadiazoles include 2,5-bis(tert-octyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-nonyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-decyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-undecyldithio)-1,3,4-thiadiazole, 2,5-bis(tert-dodecyldithio)-1,3,4-thiadiazole, or mixtures thereof.

The corrosion inhibitor may be used alone or in combination with two, three or more corrosion inhibitors. In one embodiment the corrosion inhibitor includes a mixture of (i) a 2,5-bis(alkyl-dithio)-1,3,4-thiadiazole, (ii) a benzotriazole containing a hydrocarbyl substitution on at least one of the following ring positions 4- or 5- or 6- or 7-, and (iii) a benzotriazole containing a hydrocarbyl substitution (typically a benzotriazole further reacted with an aldehyde and an amine) on at least one of the following ring positions, 1- or 2-.

In different embodiments the corrosion inhibitor is present in ranges including about 0.0001 wt % to about 5 wt %, or about 0.0001 wt % to about 0.5 wt %, or about 0.0001 wt % to about 0.1 wt %, or about 0.0005 wt % to about 0.06 wt % of the lubricating composition.

Oils of Lubricating Viscosity

The lubricating composition comprises an oil of lubricating viscosity. Such oils include natural and synthetic oils, oil derived from hydrocracking, hydrogenation, and hydrofinishing, unrefined, refined and re-refined oils and mixtures thereof.

Unrefined oils are those obtained directly from a natural or synthetic source generally without (or with little) further purification treatment.

Refined oils are similar to the unrefined oils except they have been further treated in one or more purification steps to improve one or more properties. Purification techniques are known in the art and include solvent extraction, secondary distillation, acid or base extraction, filtration, percolation and the like.

Re-refined oils are also known as reclaimed or reprocessed oils, and are obtained by processes similar to those used to obtain refined oils and often are additionally processed by techniques directed to removal of spent additives and oil breakdown products.

Natural oils useful in making the inventive lubricants include animal oils, vegetable oils (e.g., castor oil, lard oil), mineral lubricating oils such as liquid petroleum oils and solvent-treated or acid-treated mineral lubricating oils of the paraffinic, naphthenic or mixed paraffinic-naphthenic types and oils derived from coal or shale or mixtures thereof.

Synthetic lubricating oils are useful and include hydrocarbon oils such as polymerised and interpolymerised olefins (e.g., polybutylenes, polypropylenes, propyleneisobutylene copolymers); poly(1-hexenes), poly(1-octenes), poly(1-decenes), and mixtures thereof; alkyl-benzenes (e.g. dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di-(2-ethylhexyl)-benzenes); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenyls); alkylated diphenyl ethers and alkylated diphenyl sulphides and the derivatives, analogs and homologs thereof or mixtures thereof.

Other synthetic lubricating oils include polyol esters (such as Priolube® 3970), diesters, liquid esters of phosphorus-containing acids (e.g., tricresyl phosphate, trioctyl phosphate, and the diethyl ester of decane phosphonic acid), or polymeric tetrahydrofurans. Synthetic oils include those produced by Fischer-Tropsch reactions and typically may be hydroisomerised Fischer-Tropsch hydrocarbons or waxes. In one embodiment oils include those prepared by a Fischer-Tropsch gas-to-liquid synthetic procedure as well as other gas-to-liquid oils.

Oils of lubricating viscosity may also be defined as specified in the American Petroleum Institute (API) Base Oil Interchangeability Guidelines. The five base oil groups are as follows: Group I (sulphur content>0.03 wt %, and/or <90 wt % saturates, viscosity index 80-120); Group II (sulphur content≦0.03 wt %, and ≧90 wt % saturates, viscosity index 80-120); Group III (sulphur content≦0.03 wt %, and ≧90 wt % saturates, viscosity index≧120); Group IV (all polyalphaolefins (PAOs)); and Group V (all others not included in Groups I, II, III, or IV). The oil of lubricating viscosity comprises an API Group I, Group II, Group III, Group IV, Group V oil or mixtures thereof. Often the oil of lubricating viscosity is an API Group I, Group II, Group III, Group IV oil or mixtures thereof. Alternatively the oil of lubricating viscosity is often an API Group II, Group III or Group IV oil or mixtures thereof.

The amount of the oil of lubricating viscosity present is typically the balance remaining after subtracting from 100 wt % the sum of the amount of the polymer, the antiwear agent, the corrosion inhibitor and other performance additives.

The lubricating composition may be in the form of a concentrate and/or a fully formulated lubricant. If the dispersant, the antioxidant and the corrosion inhibitor are in the form of a concentrate (which may be combined with additional oil to form, in whole or in part, a finished lubricant), the ratio of the components (a), (b) and (c) (i.e. the dispersant, the antioxidant and the corrosion inhibitor to the oil of lubricating viscosity and/or to diluent oil include the ranges of about 1:99 to about 99:1 by weight, or about 80:20 to about 10:90 by weight.

Other Performance Additives

The composition of the invention optionally further includes at least one other performance additive. The other performance additives include antiwear agents, viscosity index improvers (that is viscosity modifiers), foam inhibitors, demulsifiers, pour point depressants, foam inhibitors, a carboxylic acid or anhydride, and mixtures thereof.

The total combined amount of the other performance additive compounds present on an oil free basis may include ranges of 0 wt % to about 10 wt %, or about 0 wt % to about 5 wt %, or about 0.005 wt % to about 4 wt %, or about 0.05 wt % to about 2.5 wt %, or about 0.1 wt % to about 1.5 wt % of the composition. Although one or more of the other performance additives may be present, it is common for the other performance additives to be present in different amounts relative to each other.

Antiwear Agent

In one embodiment the antiwear agent comprises a phosphorus-containing acid, salt or ester, or mixtures thereof. In one embodiment the antiwear agent is in the form of a mixture.

The antiwear agent includes those derived from phosphoric acid, phosphorous acid, thiophosphoric acid, thiophosphorous acid, or mixtures thereof.

In one embodiment the antiwear agent includes (i) a non-ionic phosphorus compound; (ii) an amine salt of a phosphorus compound; or (iii) an ammonium salt of a phosphorus compound.

In one embodiment the antiwear agent comprises an ammonium or amine salt of a phosphorus-containing acid or ester.

The amine salt of a phosphorus acid or ester includes phosphoric acid esters and amine salts thereof; dialkyldithiophosphoric acid esters and amine salts thereof; amine salts of phosphites; and amine salts of phosphorus-containing carboxylic esters, ethers, and amides; and mixtures thereof.

The amine salt of a phosphorus acid or ester may be used alone or in combination.

In one embodiment the amine salt of a phosphorus acid or ester includes a partial amine salt, or a partial amine-metal salt compound or mixtures thereof. In one embodiment the amine salt of a phosphorus acid or ester further contains a sulphur atom in the molecule.

The amine salt may be prepared from amines that include primary amines, secondary amines, tertiary amines, and mixtures thereof. The amines include those with at least one hydrocarbyl group, or, in certain embodiments, two or three hydrocarbyl groups. In different embodiments the hydrocarbyl groups contain about 2 to about 30, or about 8 to about 26, or about 10 to about 20, or about 13 to about 19 carbon atoms.

Primary amines include ethylamine, propylamine, butylamine, 2-ethylhexylamine, octylamine, and dodecylamine, as well as such fatty amines as n-octylamine, n-decylamine, n-dodecylamine, n-tetradecylamine, n-hexadecylamine, n-octadecylamine and oleyamine. Other useful fatty amines include commercially available fatty amines such as “Armeen®” amines (products available from Akzo Chemicals, Chicago, Ill.), such as Armeen C, Armeen O, Armeen OL, Armeen T, Armeen HT, Armeen S and Armeen SD, wherein the letter designation relates to the fatty group, such as coco, oleyl, tallow, or stearyl groups.

Examples of suitable secondary amines include dimethylamine, diethylamine, dipropylamine, dibutylamine, diamylamine, dihexylamine, diheptylamine, methylethylamine, ethylbutylamine and ethylamylamine. The secondary amines also include cyclic amines such as piperidine, piperazine and morpholine.

The amine may also be a tertiary-aliphatic primary amine. The aliphatic group on the tertiary-aliphatic primary amine in different embodiments contains about 4 to about 30, or about 6 to about 26, or about 8 to about 24 carbon atoms. Tertiary alkyl amines include monoamines such as tert-butylamine, tert-hexylamine, 1-methyl-1-amino-cyclohexane, tert-octylamine, tert-decylamine, tertdodecylamine, tert-tetradecylamine, tert-hexadecylamine, tert-octadecylamine, tert-tetracosanylamine, and tert-octacosanylamine.

In one embodiment the amine salt of a phosphorus acid or ester includes an amine with about C₁₁ to about C₁₄ tertiary alkyl primary groups or mixtures thereof. In one embodiment the amine salt of a phosphorus compound includes an amine with about C₁₄ to about C₁₈ tertiary alkyl primary amines or mixtures thereof. In one embodiment the amine salt of a phosphorus compound includes an amine with about C₁₈ to about C₂₂ tertiary alkyl primary amines or mixtures thereof.

Mixtures of amines may also be used in the invention. In one embodiment a useful mixture of amines is “Primene® 81R” and “Primene® JMT.” Primene® 81R and Primene® JMT (both produced and sold by Rohm & Haas) are mixtures of C₁₁ to C₁₄ tertiary alkyl primary amines and C₁₈ to C₂₂ tertiary alkyl primary amines respectively.

In one embodiment the amine salt of a phosphorus acid or ester is the reaction product of a C₁₄ to C₁₈ alkylated phosphoric acid with Primene® 81R (produced and sold by Rohm & Haas) which is a mixture of C₁₁ to C₁₄ tertiary alkyl primary amines.

Examples of the amine salt of a phosphorus acid or ester include the reaction product(s) of isopropyl, methyl-amyl (1,3-dimethylbutyl or mixtures thereof), 2-ethylhexyl, heptyl, octyl, nonyl, decyl, dodecyl, butadecyl, hexadecyl, octadecyl or eicosyl phosphoric (or dithiophosphoric) acids with ethylene diamine, morpholine, 2-ethylhexyl amine or Primene® 81R, and mixtures thereof. In one embodiment the antiwear agent comprises an amine salt of a phosphorus acid or ester or mixtures thereof. In one embodiment the phosphorus acid or ester is a C₁₄-C₁₈-alkyl phosphorus acid or ester with Primene® 81R or 2-ethylhexyl amine.

In one embodiment the dithiophosphoric acids include those reacted with an epoxide or a glycol. This reaction product is further reacted with a phosphorus acid, anhydride, or lower ester. The epoxide includes an aliphatic epoxide or a styrene oxide. Examples of useful epoxides include ethylene oxide, propylene oxide, butene oxide, octene oxide, dodecene oxide, styrene oxide and the like. In one embodiment the epoxide is propylene oxide. The glycols include aliphatic glycols, wherein the aliphatic groups of the glycols in different embodiments have about 2 to about 12, or about 2 to about 6, or about 2 to about 3 carbon atoms. The dithiophosphoric acids, glycols, epoxides, inorganic phosphorus reagents and methods of reacting the same, are described in U.S. Pat. Nos. 3,197,405 and 3,544,465. The resulting acids may then be salted with amines. An example of a suitable dithiophosphoric acid is prepared by adding phosphorus pentoxide (about 64 grams) at about 58° C. over a period of about 45 minutes to about 514 grams of hydroxypropyl O,O′-di(1,3-dimethylbutyl)phosphorodithioate (prepared by reacting di(1,3-dimethylbutyl)-phosphorodithioic acid with about 1.3 moles of propylene oxide at about 25° C.). The mixture is heated at about 75° C. for about 2.5 hours, mixed with diatomaceous earth and filtered at about 70° C. The filtrate contains about 11.8% by weight phosphorus, about 15.2% by weight sulphur, and has an acid number of about 87 (bromophenol blue).

In one embodiment the antiwear agent comprises an amide-containing dithiophosphorus acid ester. A more detailed description for the amide-containing dithiophosphorus acid ester is found in U.S. Pat. No. 4,938,884. A description of the molecular structure is found in column 2, lines 4 to 28. Suitable examples prepared are disclosed in Examples 1 to 7 (column 8, line 45 to column 10, line 13 of U.S. Pat. No. 4,938,884). Typically the amide-containing dithiophosphorus acid ester is prepared by the addition of dithiophosphoric acid to an acrylamide, such as acrylamide, methacrylamide, methylenebisacrylamide, or methylenebismethacrylamide. In one embodiment the amide-containing dithiophosphorus acid ester includes a methylenebisacrylamide, or methylenebismethacrylamide product prepared from prepared by the addition of a dithiophosphoric acid to acrylamide to form an adduct; and subsequent reaction of the adduct with formaldehyde to make the methylene coupled product.

In one embodiment the antiwear agent comprises a carboxylic acid-containing dithiophosphorus acid ester, for example 3-(bis-pentoxy-thiophosphorylsulphanyl)-propionic acid methyl ester, 3-(dibutoxy-thiophosphorylsulphanyl)-propionic acid methyl ester, or mixtures thereof

In one embodiment the antiwear agent comprises a non-ionic phosphorus compound. Typically the phosphorus atom in the non-ionic phosphorus compound may have an oxidation state of +3 or +5. The different embodiments comprise phosphite ester, phosphate esters, or mixtures thereof.

In one embodiment the antiwear agent includes a non-ionic phosphorus compound that is a hydrocarbyl phosphite. The hydrocarbyl-substituted phosphite of the invention includes those represented by the formula:

wherein each R′″ independently is hydrogen or a hydrocarbyl group, with the proviso that at least one of the R′″ groups is hydrocarbyl.

Each hydrocarbyl group of R′″ in different embodiments contains at least about 2, or at least about 4 carbon atoms. Typically, the combined total sum of carbon atoms present on both R′″ groups is less than about 45, or is less than about 35, or is less than about 25. Examples of suitable ranges for the number of carbon atoms present on R′″ groups include about 2 to about 40, about 3 to about 24, or about 4 to about 20. Examples of suitable hydrocarbyl groups include propyl, butyl, t-butyl, pentyl, hexyl, dodecyl, butadecyl, hexadecyl, or octadecyl groups. Generally the hydrocarbyl phosphite is soluble or at least dispersible in oil. In one embodiment the hydrocarbyl phosphite is di-butyl hydrogen phosphite or a C₁₆₋₁₈ alkyl or di-alkyl hydrogen phosphite. A more detailed description of the non-ionic phosphorus compound is included in column 9, line 48 to column 11, line 8 of U.S. Pat. No. 6,103,673.

In one embodiment the antiwear agent includes a phosphate ester. Examples of a suitable phosphate ester include triaryl phosphates such as tricresyl phosphate, triphenyl phosphate, tri-dimethylphenyl phosphate, tri-butylphenyl phosphate, or mixtures thereof.

In one embodiment the antiwear agent includes a thiophosphate ester. Examples of a suitable thiophosphate ester include triaryl thiophosphates such as tricresyl thiophosphate, triphenyl thiophosphate, tri-dimethylphenyl thiophosphate, tri-butylphenyl thiophosphate, or mixtures thereof.

In different embodiments the antiwear agent is present in ranges including about 0 wt % to about 5 wt %, or about 0.001 wt % to about 2 wt %, or about 0.05 wt % to about 1.5 wt %, or about 0.1 wt % to about 1 wt % of the lubricating composition.

Viscosity Modifiers

Viscosity modifiers include hydrogenated copolymers of styrene-butadiene, ethylene-propylene copolymers, polyisobutenes, hydrogenated styrene-isoprene copolymers, hydrogenated isoprene polymers, polymethacrylate, polyacrylate, polyalkyl styrenes, hydrogenated alkenyl aryl conjugated diene copolymers, polyolefins, and esters of maleic anhydride-styrene copolymers.

Other performance additives such as foam inhibitors including copolymers of ethyl acrylate and 2-ethylhexylacrylate and optionally vinyl acetate; demulsifiers including trialkyl phosphates, polyethylene glycols, polyethylene oxides, polypropylene oxides and (ethylene oxide-propylene oxide) polymers; pour point depressants including esters of maleic anhydride-styrene copolymers, polymethacrylates, polyacrylates or polyacrylamides; and seal swell agents including Exxon Necton-37™ (FN 1380) and Exxon Mineral Seal Oil (FN 3200); and dispersant viscosity modifiers (often referred to as DVM) include functionalised polyolefins, for example, ethylene-propylene copolymers that have been functionalized with the reaction product of maleic anhydride and an amine, a polymethacrylate functionalised with an amine, or styrene-maleic anhydride copolymers reacted with an amine; may also be used in the composition of the invention.

INDUSTRIAL APPLICATION

The method of the invention is useful for lubricating a mechanical device typically requiring a working fluid, a hydraulic fluid, a circulating oil or a turbine oil.

In one embodiment the mechanical device requires a fluid selected from the group consisting of a working fluid, a hydraulic fluid, a circulating oil, a turbine oil and mixtures thereof.

In different embodiments the mechanical device is a hydraulic system, a turbine system, or a circulating oil system.

The following examples provide illustrations of the invention. These examples are non exhaustive and are not intended to limit the scope of the invention.

EXAMPLES Lubricating Compositions EX1 to EX5

A series of lubricating compositions are prepared containing the following additives: a borated dispersant, an amine salt of a phosphorus compound, a mixture of phenolic and aminic antioxidants, two or more corrosion inhibitors, and antifoam agents. The combined total treat-rate of all the additives (on an oil-free basis, i.e. excluding normal amount of diluent oil commonly associated with each additive) is about 1.47 wt % for Example 1 (EX1), about 1.48 wt % for Example 2 (EX2), about 1.76 wt % for Example 3 (EX3), about 1.40 wt % for Example 4 (EX4) and about 1.27 wt % for Example 5 (EX5).

Examples EX1 to EX5 are evaluated in the following tests: (i) oxidation stability of steam turbine oils using ASTM Method D2272, (ii) kinematic viscosity at about 40° C. using ASTM method D445, and (iii) thermal stability of hydraulic fluids after heat stressing of the fluid utilising the “Cincinnati Machine Thermal Stability Test” Procedure A. The Cincinnati Machine Thermal Stability Test evaluates steel and copper corrosion and thermal stability.

The data obtained for tests (i) and (ii) are shown in Table 1. The data obtained for test (iii) are shown in Table 2.

TABLE 1 Test (ASTM Method) EX1 EX2 EX3 EX4 EX5 D2272 (minutes) 211 222 248 215 268 D445 (mm²/s) 32.74 32.75 32.95 32.85 32.84

TABLE 2 Cincinnati Machine Thermal Stability Test EX1 EX2 EX3 EX4 EX5 Copper Rating 3 3 3 4 5 Copper weight loss (mg) 0.7 1.2 0.2 −2.7 0 Steel Rating 1 1 1 1 1 Steel weight loss (mg) 0.2 0.4 0.1 0 0.3 Sludge Formed (mg/100 ml of oil) 0.95 11 0.65 0.6 3.6

The data obtained indicate that the lubricating compositions of the invention are capable of providing a hydraulic fluid, turbine oil or circulating oil with at least one of acceptable sludge performance, acceptable thermal stability and acceptable oxidation stability.

While the invention has been explained in relation to its various embodiments, it is to be understood that various modifications thereof will become apparent to those skilled in the art upon reading the specification. Therefore, it is to be understood that the invention disclosed herein is intended to cover such modifications as fall within the scope of the appended claims. 

What is claimed is:
 1. A method for lubricating a hydraulic system comprising supplying to the hydraulic an ashless lubricating composition comprising: (a) about 0.01 to about 2 wt % of a dispersant; (b) about 0.05 to about 1 wt % of an antioxidant; (c) about 0.0001 wt % to about 0.1 wt % of a corrosion inhibitor; (d) an oil of lubricating viscosity; and (e) about 0.05 wt % to about 5 wt % of an antiwear agent mixture comprising: (i) an ammonium or amine salt of a phosphorus-containing acid or ester, and (ii) an amide-containing dithiophosphorus acid ester.
 2. The method of claim 1, wherein the dispersant is a borated dispersant.
 3. The method of claim 1, wherein the antioxidant comprises (i) a hindered phenol or (ii) an alkylated diphenylamine.
 4. The method of claim 1, wherein the corrosion inhibitor comprises (i) a 2,5-bis(alkyl-dithio)-1,3,4-thiadiazole, (ii) a benzotriazole containing a hydrocarbyl substitution on at least one of the following ring positions 4- or 5- or 6- or 7-, or (iii) a benzotriazole containing a hydrocarbyl substitution on at least one of the following ring positions 1- or 2-.
 5. The method of claim 1, wherein the lubricating composition further comprises about 0.05 wt % to about 1.5 wt % of an antiwear agent.
 6. The method of claim 1, wherein the amide-containing dithiophosphorus acid ester is prepared by the addition of dithiophosphoric acid to an acrylamide chosen from acrylamide, methacrylamide, methylenebisacrylamide, or methylenebismethacrylamide.
 7. The method of claim 1, wherein the amide-containing dithiophosphorus acid ester is a methylenebisacrylamide, or methylenebismethacrylamide product prepared from prepared by the addition of a dithiophosphoric acid to acrylamide or methacryalamide to form an adduct; and subsequent reaction of the adduct with formaldehyde to make the amide-containing dithiophosphorus acid ester. 